The present invention relates to a method for lining a pipe conduit or a duct by way of a sealing inner lining with a flexible tubing.
A method for lining the inner surface of a pipe conduit with a flexible-tubing-like lining material whilst using a fluid resin serving as adhesive is disclosed in U.S. Pat. No. 4,368,091. This method comprises the following steps:    a) filling a metered quantity of the resin into the flexible-tubing-like lining material with a uniform distribution over its length,    b) annularly fastening the one end of the lining material containing the fluid resin in its inside, to the one end of the pipe conduit,    c) exerting a pressure onto the lining material with the help of a pressure medium, in a manner such that this is turned inside out at a turning point which is formed behind the fastening location, so that the lining material moves into the pipe conduit and the turning point advances in the movement direction into the pipe conduit, wherein the turned lining material with its surface coated with resin is pressed onto the inner surface of the pipe conduit, and    d) maintaining the pressure by the medium, until the resin is cured.
With these known methods, one strives to use as long as possible flexible tubings as lining materials, so that one needs only to create as few as possible access possibilities to the inside of the pipe conduit or of the duct. Thus it is already possible to introduce flexible tubings of more than 500 m length into the pipe conduits or ducts. This however is a multi-hour procedure, wherein the filling and distribution of the adhesive alone (about 1000 kg with a normal diameter of DN 300 and a renovation length of 600 m) demands more than an hour and the average advance speed of the flexible tubing is about six meters per minute. The applied adhesive must be well workable up to the completion of the lining pressure, i.e. have a pot time (duration of the workability) of several hours.
The curing time with cold curing is usually at least fivefold the pot life, so that the pressure medium must remain in the flexible tubing for more than a complete day, until the adhesive has been adequately cured. Since with the renovation of a pipe conduit or of a duct effected in this manner, the normal operation must be interrupted for this duration, this entails significant operational limitation. A shortening of the curing time by way of heating the pressure medium requires some effort and is a problem at least with a renovation of pipe conduits of steel, inasmuch as the pipe conduit should not be heated to temperatures greater than 30° C., since otherwise breakage of the welding seam may occur due to thermal stresses, and outer bituminous corrosion encasings may be damaged. Technical difficulties which may hardly be overcome at all occur with pipe conduits of large lengths and large diameters.
Basically however, by way of shortening the curing time, pipe conduits should be taken out of operation, cleaned, lined with the flexible tubing and put back into operation again in one day. With this, one may make do without emergency conduits for maintaining the supply, which require effort and are expensive.
For this reason, a method is known from U.S. 2006/0254711 A1, with which the filled adhesive firstly has a long curing time, after introduction of the flexible tubing into the pipe conduit however is subjected to a radiation with UV-rays, IR-rays microwaves and/or ultrasound, by way of which it cures in a shorter time. For this, at least one radiation unit in the activated condition is pulled through the introduced flexible tubing, which is pressed by way of an adequate inner pressure onto the inner wall of the pipe conduit. This may be effected in a manner such that firstly the flexible tubing is introduced into the pipe with a speed which is controlled by a retaining strap led through the inside of the flexible tubing, after the introduction, the connection of the flexible tubing to the retaining strap is separated at the end which is at the front in the movement direction of the flexible tubing, the radiation unit is coupled to the separated-away end of the retaining strap and in the activated condition is pulled by way of the retaining strap through the flexible tubing to its end which is at the rear in the movement direction. Thereby, the retaining strap is pulled from the rotation drum which is envisaged for the flexible tubing, before its introduction into the pipe conduit and is wound onto this.
This method however has the disadvantage that the rotation drum usually has no controllable winding up speed. This however is absolutely necessary, in order to achieve the desired degree of curing of the adhesive which is dependent on the radiation duration. A later retrofitting of the rotation drum for a controllable winding-up speed on the other hand requires some effort, since the rotation drum has considerable dimensions and must be built in a sturdy manner. This results from the fact that it must receive and wind-off a flexible tubing with filled-in plastic, with a length of several hundred meters. Moreover, given a constant winding-up rotational speed, the pull speed changes during the winding up procedure due to the change of the winding diameter.
Moreover, the danger may exist that as a result of an unforeseen narrowing of the free pipe cross section, the radiation unit remains stuck in the pipe and may not be pulled any further. One must then locate the narrowed location and an external entrance to the tube must be created, and the pipe must be opened from the outside, in order to recover the radiation unit and subsequently repair it. This is an extremely tiresome and expensive procedure.